I assume it's a SOLI INVICTO reverse. Could that be an R over X in the left field? Perhaps like?:
http://www.constantinethegreatcoins...L_Rome27.jpg
https://www.acsearch.info/search.html?id=1819219
Hopefully some of the Roman specialists will contribute.
http://www.constantinethegreatcoins...L_Rome27.jpg
https://www.acsearch.info/search.html?id=1819219
Hopefully some of the Roman specialists will contribute.























